TACHINID PARASITES OF THE GIPSY MOTH. 
225 
rounded out, is not done away with. Unless the parasite hibernates 
in the brown-tail caterpillars such a hosl must be found among the 
native Lepidoptera, and while the number of species available prob- 
ably runs into the hundreds, the}" are, with few exceptions, already 
controlled by their native parasites. Compsilura, if it continues to 
increase, will have to overcome these parasites in the competitive 
struggle for possession, and, as already stated, the outcome of this 
struggle is awaited with interest. Upon it will very Largely depend 
the effectiveness of Compsilura as a parasite of the gipsy moth and 
the brown-tail moth in America. 
TACHINA LABVABUM L. 
This rather important parasite of the gipsy moth (fig. 43), and to a 
more limited extent of the brown-tail moth in Europe, is so simi- 
lar to the Ameri- 
can Tachina nulla 
Walk, as to make 
the separation of 
the two by struc- 
tural characters 
alone difficult at 
best , and in some 
instances impossi- 
ble. It is similarly 
closely allied to 
T a ch ina japonica 
Tm\\ iis., and the 
three species or 
races appear to oc- 
cupy about the 
same position in 
the natural order 
of things in the several countries which they inhabit. The European 
and the American are both quite catholic in their host relations, and 
while the same can not be said of the Japanese in the present state 
of our knowledge 4 , it will doubtless be found true when this knowledge 
shall be m< >re extensive. 
From an economic standpoint Tachina nulla and Tachina larvarum 
are distinct enough specifically, if we are to consider their parasitism 
from an economic aspect, since the one is habitually and commonly a 
parasite of the gipsy moth, while the other is not. It would appear that 
Tachina mella attacks the gipsy moth quite as freely in America as 
Tachina larvarum does in Europe, but, as has already been mentioned, 
the attack is not successful from either the economist's or the parasite's 
point of view. 
95677°— Bull. 01—11 15 
Fig. 43. — Tachina lartarum: Adult female and head in profile. Enlarged. 
(Original.) 
